topic Re: One-sided Proc GLM with testvalue in Statistical Procedures

One-sided Proc GLM with testvalue

nsns — Mon, 23 Jun 2025 14:53:11 GMT

Hi .

What is the correct code using Proc GLM to test a 2-groups one-sided hypothesis where the hypothesis is H0: Difference between groups <= 4, H1: Difference between groups > 4? The model will include baseline and site as covariates.

Thanks.

Re: One-sided Proc GLM with testvalue

StatDave — Mon, 23 Jun 2025 15:31:35 GMT

See this note on one-sided testing and using a non-zero null value. For example, you can PROC ORTHOREG which is the modern regression procedure that has the most up-to-date capabilities available, including the LSMESTIMATE statement that allows you to estimate and compare means and to specify a null value other than zero (TESTVALUE=) and one-sided tests (UPPER and LOWER). See the ORTHOREG documentation for details. For example, the following tests whether the difference between the F and A drugs exceeds 4.

data DrugTest;
   input Drug $ PreTreatment PostTreatment @@;
   datalines;
A 11  6   A  8  0   A  5  2   A 14  8   A 19 11
A  6  4   A 10 13   A  6  1   A 11  8   A  3  0
D  6  0   D  6  2   D  7  3   D  8  1   D 18 18
D  8  4   D 19 14   D  8  9   D  5  1   D 15  9
F 16 13   F 13 10   F 11 18   F  9  5   F 21 23
F 16 12   F 12  5   F 12 16   F  7  1   F 12 20
;
proc orthoreg data=DrugTest;
   class Drug;
   model PostTreatment = Drug PreTreatment;
   lsmestimate Drug 'F-A>4' -1 0 1 / testvalue=1 upper;
run;

Re: One-sided Proc GLM with testvalue

nsns — Mon, 23 Jun 2025 16:28:59 GMT

Thank you.

This looks great - thank you.

I compared the estimates to the estimates of the Proc GLM and they were the same.

(In the code below, Should the testvalue=4 in the lsmestimate line?)

Re: One-sided Proc GLM with testvalue

StatDave — Mon, 23 Jun 2025 16:34:45 GMT

Yes, sorry, I had just been using 1 initially.

Re: One-sided Proc GLM with testvalue

nsns — Mon, 23 Jun 2025 16:36:24 GMT

All good. Thank you so much for your help.